The present invention relates in general to a cotton gin, and more particularly to a roller cotton gin constructed to strip lint from the seed of seed cotton with a high degree of efficiency and having high capacity.
The ginning of cotton, which is the operation in which the seeds are separated from the cotton fibers, is customarily carried out either in a saw gin or in a roller gin. The saw gin has been the dominant type for ginning the fuzzy seed Upland Cotton while the saw gin has not been acceptable for use on the Black Seed Cotton which generally has a longer staple. When ginning the extra long staple Black Seed Cottons, which are commonly referred to as a variation of Egyptian Cottons, on saw gin fiber, breakage results in a shorter staple and generally a less desirable fiber for the high-quality products for which this fiber is normally used.
To generally distinguish between these two basic types of cotton, by far the most common type of cotton is the Upland Cotton which varies in staple length from less than 3/4 inch to more than 11/8 inch. The seeds are fuzzy and each fiber is firmly attached to the seed. The cotton is almost always saw ginned, although there are periodic efforts to roller gin the longer staple varieties to better preserve the fiber quality.
The other type of cotton is sometimes referred to as Black Seed Cotton, but more commonly referred to as extra long staple cotton. The staple length of this cotton varies widely as with the Upland Cotton but the more common varieties are about 13/8 inch to 11/2 inch in staple length. The fibers are very fine and silky and can be used in very expensive materials. Saw gins break and tangle these fine fibers which lowers their quality. Also, the fibers are so gently attached to the slick surface of the seed, the performance of the saw gin is not very satisfactory. For these reasons, this Black Seed Cotton is almost always roller ginned.
A particular disadvantage has been encountered heretofore in connection with roller gins in that, whereas a saw gin produces fibers continuously, roller gins heretofore used are somewhat intermittent in operation. This occurs because of the fact that there is a reciprocating blade employed that cooperates with the ginning roller and a stationary doctor knife to strip the seeds from the fibers as the fibers are drawn past the doctor knife by the ginning roller. The reciprocation of the moving blade serves to interrupt the flow of cotton to the ginning roller so that in this type of roller gin, the productive rate of the roller gin has been relatively slow. The high quality of the fibers produced by a roller gin, however, have caused it to continue in use, particularly in regions where the cotton is characterized by particularly long fibers.
Various attempts have been made to improve the roller cotton gin and, in particular, to improve the gin with respect to the rate of fiber production in order to reduce the cost of ginning the Black Seed Cotton, while at the same time retaining the advantageous characteristics of the roller gin that the fibers produced are not entangled or broken.
Much effort has been given to alleviating difficulties with the length of time required in roller gins to pull the fibers from the seed, particularly long fibers, and to dislodge the seed from the fibers with the seeds in a relatively fiber-free condition, and do this continuously at a relatively high rate of speed. This has led to the construction of a roller gin having a ginning roller turning against a stationary knife so that the fibers will be drawn under the knife while the seeds are retained, and utilizing with this construction rotary or continuously moving knife means to knock the seeds away from the stationary knife. Difficulties have been encountered however in producing clean seeds with this construction because not enough ginning time was given to pull the fibers off the seeds and some considerable seed cracking occurred.
In the case of roller gin employing a reciprocating blade for the purpose of disloding the seeds from the stationary knife, it has been proposed to have the moving blade overlap the stationary knife by about 1/2 the length of the staple of the cotton being ginned. Fibers are pulled, by friction of the ginning roller, under the knife until the seed is against the knife edge. The friction is not always great enough to pull all the fibers from the seed, in which case it is necessary for the blade to push the seed away from the knife's edge. In the case of the reciprocating blade, it operates parallel and close to the top surface of the blade to push the seed away. If the seed is not pushed beyond the length of most of the fibers, the friction on the fibers still held between the roller and the knife will draw the seed back to the knife, at which time most if not all the fibers are removed. It is difficult to determine accurately how many times an individual seed returns before all fibers are removed, as this depends on a number of variables, the most obvious one being the pressure of the ginning roller against the knife. The pressure can be enough for the friction to remove practically all the fibers as the seeds are pushed away by the blade. However, such pressure will usually cause the roll to overheat.
The overlap of the reciprocating blade of approximately one half the staple length has been accepted by those experienced in ginning extra long staple cottons for many years. The fact that the reciprocating blade completely blocks the access of the cotton to the ginning roller during its travel across the knife limits the capacity of such a method drastically. The economics of this method limit its use to the very longest staple of high quality whose value would be greatly reduced by saw ginning.
Literally hundreds of roller ginning machines have been designed in an effort to increase the capacity and thus reduce the cost of roller ginning. In spite of these efforts the reciprocating blade method prevailed through the 1950's. Subsequently, as a result of work by some engineers engaged in a program to prove methods of roller ginning at the United States Department of Agriculture's Ginning Laboratory at Mesilla Park, N. Mex., there appeared in about 1961 a roller gin design using square bars mounted on a driven chain system to travel over a knife, allowing the cotton to be fed to the ginning roller between the bars. This was called "the flight bar gin". Several companies manufactured and installed elaborate and expensive plants using the flight bar gin principle, but these plants were not successful, because it was not possible to maintain the required pressure on the flight bars as they moved over the knife, since sprocket and chain wear necessitated constant adjustment.
In analyzing the difficulties encountered with the flight bar gin and studying the art, I concluded that a rotating blade would serve the same purpose as the flight bar or the old reciprocating bar and permit attainment of improved roller ginning. Study of the art showed that rotating blades, such as blades on a rotating cylinder, had been previously tried and found to be unsuccessful, but the rotating cylinders with blades in those cases were approximately the diameter of the ginning roller which allowed for an overlap much greater than the staple length. I determined that many of the problems previously encountered with such large diameter rotating blades or with the flight bars should be alleviated by using a rotating blade about 23/4 inches in diameter and an overlap with the knife of about 3/4 inch and a number of roller gins having this dimensional relationship and arrangement have been previously used for cottons having a staple length of, for example, about 13/8 inch to 1 1/2 inch.
I have devoted considerable study to investigation of the optimum diameter, speed and configuration of the rotating blade device and the overlap, particularly with regard to roller ginning of the shorter staple cotton. My studies indicate that for Upland Cotton, the blade device should be about 2 inches in diameter to achieve optimum release of the seed after about 1/2 inch to 5/8 inch movement. In considering the configuration to maintain the required rigidity with such a small diameter blade and the number of blades to be provided, the R.P.M. is a factor. A study of the relationship of the surface speed of the rotating blade to that of the ginning roller indicates that the ratio should approach 1:1. If the ginning roller, as it approaches the ginning point, is fully covered with cotton, and the surface speed of the rotating blade is significantly less than that of the ginning roller, there would be intermittent build-ups of cotton ahead of the rotating blade as each blade comes into ginning position. These build-ups overload the ginning capacity of the ginning roller intermittently, resulting in the necessity to cut back the feed. The build-ups can be eliminated by setting up the surface speeds of the ginning roller and rotating blade to be close to the same speed.
With this established, the question of the number of blades on the rotating blade assembly can be determined within reasonable limits. As the seed is pushed away from the ginning point to the release position it must have time to return to the ginning point before the next blade moves to the ginning point. The travel of the ginning roller surface must be enough to pull the seed back to the knife before the next blade reaches the knife edge.
It has been determined that for Upland Cotton, a rotating blade assembly of about 2 inches in diameter and having four blade points or blade members more nearly meet this criteria. As one means of achieving this in a simple manner, I have used a 11/2 inch by 11/2 inch square cross section bar which is machined to a configuration to provide four blade formations at the four corners by providing a V-cut vein or groove spanning the axial length of the bar immediately adjacent each of the four corners on the side thereof in the direction of rotation of the rotating blade assembly. The diagonal dimension of this square bar is 2.12 inches, which is very close to the calculated 2 inch diameter determined to be appropriate to meet these criteria. This grooved square cross section rotating blade or rotobar, when arranged adjacent the ginning roller and the stationary knife, has shown capacities which are much superior to any obtained on prior units, particularly where a reasonably low residual lint on the seed is maintained. By this arrangement, the rotating blades formation at the corners of the square bar with the V-cut grooves move the seed away from the knife edge, and then allow them to return to the knife edge before the next blade hits the seed, and maintains a surface speed relationship of the two rollers that will avoid an accumulation of unginned cotton on the ginning roller ahead of the rotating blade. Of course, if more than four blades are used on the rotating blade assembly, the speed of the rotating blades has to be reduced or the speed of the ginning roller increased to avoid having the blade hit the seed before it returns to the knife edge, thus leaving lint on the seed. For extra long staple, of the order of 13/4 inch to 11/2 inch, the diameter of the four point rotating blade assembly may be increased to approximately 3 inches.
While such a roller gin with the grooved sqaure cross section rotobar or rotary blade device having approximately a 11/2 inch by 11/2 inch square cross section for Upland Cotton achieved the desired result of pushing the seed away from the ginning point to the release position and then allowing it to return to the ginning point before the next blades moves to the ginning point, to achieve high capacity ginning, it was found that a certain number of seed locks are carried over the point of contact of the stationary knife and the ginning roller surface, referred to as the pinch point, without being ginned. This was primarily due to the fact that they are carried rapidly by the blades of the rotary bar device and the fibers failed to get picked as they crossed the pinch point. These unginned locks would then be intermingled with the ginned seed and be reclaimed and returned through the system. I have discovered that by providing a pad or strip of flexible material on the flat surface of the square cross section grooved rotary bar device of such dimension as to press the seed locks against the ginning point, the percentage of unginned seed locks is drastically reduced and the capacity is increased accordingly. Preferably, use of a piece of felt or sponge rubber, for example about 1/4 inch by 5/8 inch in cross section, bonded to the center of the flat surface and spanning the length of the rotary bar device provides satisfactory results. This expedient of providing a pad of flexible material along the midregion between successive blades of a rotobar or rotating blade assembly also improves the performance of conventional rotary blade devices formed of a round center shaft and 4 or more radial blades having the flexible pads in the base region of each pocket between successive blades.
An object of the present invention, therefore, is the provision of a novel roller gin construction having a rotating blade or rotobar device of small diameter and novel construction arranged immediately adjacent the working or leading end of the stationary knife, having an appropriate configuration and surface speed and spacing between blades to move the seed away from the knife edge and then allow it to return to the knife edge before the next blade hits the seed, and maintaining the surface speed relationship between the rotating blade assembly and the ginning roller so as to avoid an accumulation of unginned cotton on the ginning roller ahead of the rotating blade.
Another object of the present invention is the provision of a novel roller gin having a rotating blade or rotobar device of small diameter relative to the diameter of the ginning roller formed of square cross section having V-shaped veins or grooves immediately adjacent the corners to define seed-engaging blades and seed receiving pockets therebetween so correlated to the seed size and to the speed of rotation of the ginning roller and the rotating blade device as to cause the seed to be pushed away from the ginning point or pinch point to a release point by engagement with the blade-like surfaces on the rotating blade device and then have time to return to the pinch point before the next blade-like surface moves to the pinch point, the release point being such that the seeds are not pushed out of the ginning zone with fibers still attached.
Yet another object of the present invention is the provision of a novel roller gin construction having a rotating blade device adjacent the edge of the stationary knife provided with plural blades transversely spanning the width of the gin formed from a square cross section member providing a blade device of small diameter compared to the diameter of the ginning roller having a surface speed close to the surface speed of the ginning roller, and having flexible pads between the successive blades to press the cotton seed locks against the ginning point and reduce the percentage of unginned locks.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating preferred embodiments of the invention.